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The Upper Triassic alkaline magmatism in the NW Iberian Chain (Spain)/El magmatismo alcalino del Triasico Superior en el NO de la Cadena Iberica (Espana).

1. Introduction

The Triassic--Jurassic transition in the NE margin of the Iberian peninsula (Spain) was characterised by a strong extensional regime (Sopena et al., 1988) related to the Iberian Rift (Alvaro et al., 1979). The extension was developed along listric normal faults, in the brittle--ductile transition zone of the continental crust (Gibbs, 1984; Wernicke and Tilke, 1989; Morley, 1999). The possible propagation in depth in a ramp-and-flat staircase fault model across the lithosphere and even the upper mantle is a possibility not to be discarded in the Iberian Plate (Vargas et al., 2009).

Alvaro et al. (1979) defined the Iberian rifting as a result of a triple junction, located over a mantle plume centred in a position close to the present-day Castellon city. Salas and Casas (1993) identified four successive evolutionary stages in the basins of the eastern Iberian margin during the Mesozoic extension. The Triassic rift (Late Permian-Hettangian) is the first of these stages; it comprised a tectonic subsidence phase followed by a long period of thermal subsidence (Lopez Gomez et al., 1993; Arche and Lopez Gomez, 1996).

An Upper Triassic alkaline magmatic province was developed at the end of the Triassic rift stage (Lago et al., 1996). This magmatic province is characterised by similar geochemical, petrological and emplacement conditions. It comprises outcrops in the NW part of the Iberian Chain (Aragonian Branch), in the Catalonian Coastal Ranges (Tarragona and Mallorca) and southern France (Corbieres, Ecrins-Pelvoux and Provence). It is associated to the intracontinental rifting of the western margin of the Neotethys, over an asthenospheric mantle source (Lago et al., 1996; Bastida et al., 1989).

The Upper Triassic alkaline magmatism in the northwestern Iberian Chain consists of a hypovolcanic complex emplaced into the Keuper facies in two geographic sectors (Fig. 1): a) the N front of the Cameros Massif (La Rioja), and b) the Moncayo Massif (Soria and Zaragoza). This complex has been partially studied by Bastida et al. (1989) and Sanz et al. (2012a). A complete study of this magmatism, however, has not been carried out up to date.

Recently, Perez-Lopez et al. (2012) have described a Norian subalkaline magmatism related to the Triassic rift in the external part of the Betic Cordillera. This magmatism emplaced into the Zamoranos Fm (Perez-Lopez et al., 1992), which is correlated to the Imon Fm (Iberian Chain) and the Isabena Fm (Pyrenees) and to other carbonate units of the western Tethys realm (Perez-Lopez et al., 1992; Lopez-Gomez et al., 1998; Arnal et al., 2002; Perez-Lopez and Perez-Valera, 2007). Outside of Iberia, Upper Triassic igneous rocks also have been recognised in SE France (e.g. Corbieres, Ecrins-Pelvoux and Provence; Azambre andRossy, 1981, Durand et al., 2011 and references therein, Vatin-Perignon et al., 1974) and the Brescian Prealps (Cassinis et al., 2008).

The aim of this paper is to characterise for the first time the Upper Triassic magmatism in the Cameros and Moncayo sectors in order to define its emplacement age and petrogenetic features. Further, the comparison with Upper Triassic magmatisms of SW Europe allows us to establish the geodynamic implications for the western margin of the Neotethys rift.

[FIGURE 1 OMITTED]

2. Stratigraphical background

The Keuper facies in the NW part of the Iberian Chain (Aragonian Branch) is mainly composed of mudstones with interbedded evaporite levels and sporadic sandstone and dolomite levels (Lopez Gomez et al, 2002). The general interpretation of the Keuper facies is that it represents sabkha deposits with more continental influence towards the west. The age of these deposits is Carnian to Norian according to pollen and spore associations (Lopez-Gomez et al., 2002 and references therein). The Keuper facies is usually overlaid by the Imon Fm (Goy and Yebenes, 1977), which comprises well-stratified dolomites showing a gradual transition from the Keuper facies, representing carbonate-evaporite tidal flat deposits of latest Norian to early Rhaetian age (Lopez- Gomez et al. 1998).

In the studied area (Figs. 2 and 3) the upper part of the Keuper facies is further subdivided into three parts (lower, middle, upper); magmatic bodies are only recognised in the middle part.

The lower part is relatively simple and shows similar features in both sectors (Cameros and Moncayo). This sequence is formed by units of red-orange compact argillites of variable thickness (up to 20 m), interbedded with siltstones and dolomite-limestone beds of cm-scale thickness (Fig. 3A and B).

The middle part is formed by a magmatic-sedimentary sequence. It is composed of several igneous layers emplaced into argillites. The thickness of this part increases from the SE (5-50 m in the Moncayo sector) to the NW (30-100 m in the Cameros sector) (Fig. 3a andb). Only one igneous unit is recognised in the Moncayo sector, whereas several igneous units crop out in the Cameros sector.

The upper part shows marked differences in the two studied sectors. In the Cameros sector (Fig. 3a) it is generally formed by a relatively thin (1 to 7 m) sequence of marly-argillites to marls and dolomite-limestone units. In the Moncayo sector (Fig. 3b) it comprises argillites, siltstones and sandstones. The sandstones consist of cm- to dm-scale beds of fine to medium grain-size with planarcross-bedding. Characteristically, different (up to 5) decimetric beds of conglomerate are recognised within the argillite units. These conglomerates include angular to sub-rounded heterometric clasts of igneous rocks, dolomites, argillites and quartzites (Fig. 4a), showing a main grain-supported texture and a vertical grain-size decrease. The clasts of igneous rocks are petrologically similar to the igneous bodies emplaced in the middle part (Lago et al., 1996). In most cases, the conglomerate beds show a lenticular to tabular geometry with channel-shaped basal surfaces of SW-NE main direction. The thickness of the conglomerate beds and the size of the clasts decrease to the SE, where comprises a decimetric microconglomeratic bed near Arandiga, within marly-argillites and centimetric dolomite beds (sections 15-17; Fig. 3b); in this case the clasts are homometric and subrounded to rounded in shape. The upper part of the Keuper facies in the Moncayo sector reaches its maximum thickness (12 m) in the western part, except for section 11 (Figs. 2 and 3b) where it is absent.

Concerning the Imon Fm, in the Cameros sector it comprises a lower part of massive grey dolomites and an upper part of dolostone breccias (Fig. 3a). In contrast, in the Moncayo sector it is preceded by a metric sequence of yellowish marls or marly-limestones with centimetric layers of interbedded massive vuggy dolostones. The Imon Fm is sometimes not present, as in the case of section 15, where the basal Lower Jurassic deposits directly overlie the Keuper facies (Fig. 3b).

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3. Field description

The studied outcrops are oriented along a NW-SE trend of cartographic scale (Fig. 2). The outcrops of the Cameros sector are located in the north-eastern part of the Cameros massif, close to the alpine North Cameros thrust front. On the other hand, the outcrops of the Moncayo sector are located near to the NW-SE Tablado-Jarque fault.

The igneous levels are grey coloured, with a purple hue at the most altered areas. They are usually concordant with the stratification and present two main directions: NNW-SSE and W-E, related to their location at the flanks of a main alpine fold ofNW-SE axis orientation (Fig. 2).

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Ten sections have been studied in the Cameros sector (Fig. 3a). The igneous levels show a tabular to irregular shape, although some folded bodies have been observed as well. The thickness of the igneous levels varies from 2 to 69 m. The number of levels recognised in each section also varies; up to three levels, separated by centimetric beds of argillites, have been recognised in the central and the southeastern part of this sector. The maximum thickness of exposed igneous rocks reaches up to 94 m in the central part of the Cameros Massif (section 4; Fig. 3a).

Seven stratigraphical sections have been studied in the Moncayo sector (Fig. 3b). In this area only one igneous body crops out per section. The igneous body is thinner (0.6 to 38 m) than the igneous bodies of the Cameros sector. The maximum thickness (38 m) corresponds to the eastern part of the Moncayo Massif (section 17; Fig. 3b).

In detail, the contact between the igneous bodies and the sedimentary host-rocks is generally irregular and characterised by a transition zone from the igneous rock to the sedimentary rock. This zone is composed of cmscale sub-rounded igneous rocks intermixed with the host-rock sediments (Fig. 4b). These structures are considered peperites as defined by White et al. (2000) and Skilling et al. (2002). Besides, sediment injections and irregular cm-scale fragments of structure-less sediments are locally observed inside the intrusions (Fig. 4c), close to their lower margin. Furthermore, a low-grade contact metamorphism has been identified in the sedimentary host-rocks at the Moncayo sector (Bastida et al., 1989).

Vesicles are frequent in the igneous rocks. They are rounded or elongated in shape, millimetric to centimetric in size and filled by calcite and quartz (Fig. 4d). In most cases, several vesicle-rich levels can be identified, oriented parallel to the contact with the host-rock.

The igneous bodies are heterogeneous and a petrological zoning can be usually established from the margin to the centre (Bastida et al., 1989): a) chilled margin facies, b) central facies and c) pegmatoid facies. The chilled margin facies includes dark-grey coloured aphanitic rocks with common vesicle-rich levels (Fig. 4d) and xenoliths. The central facies includes light-grey coloured massive igneous rocks with non oriented mm-sized phenocrysts, visible to the naked eye; most of them are black-coloured, olivine crystals (Fig. 4e). The pegmatoid facies is developed locally in the innermost areas of the intrusions. It consists of light grey, cm- to dm-scale levels which include bigger crystals than those in the central facies, up to centimetric in diameter (Fig. 4f).

In the Cameros domain, the vertical zoning of the igneous bodies is not always consistent. As explained above, the chilled margin facies is usually located at the margins and the central facies represents the centre of the igneous bodies. However, we have identified several examples where the sequence chilled margin--central facies is repeated several times, so that chilled margins are also recognised at the centre of the bodies (e.g. section 2, Fig. 3a). In other sections mechanical contacts (fault breccias composed of igneous and host-rock clasts) have been identified between different zones of the central facies (e.g. section 7, Fig. 3a).

4. Samples and methods

The stratigraphical study of the magmatism has been undertaken through 17 stratigraphic sections (1-17; Fig. 2 and 3). They are focused on the igneous rocks and include the sedimentary units over and below them as well, recording the Triassic-Jurassic transition in the study area: from the Upper-Triassic (Carnian) argillitic beds, to the Imon Fm (latest Norian to early Rhaetian; Lopez Gomez et al., 1998). Both the igneous and the sedimentary units have been studied in detail.

More than 300 rock samples were collected from the studied stratigraphic sections. They are strongly affected by spilisation that triggers alteration of the primary mineral assemblage and mobilisation of [H.sub.2]O, C[O.sub.2], Li, Rb, Sr, Ba, K and Cu (e.g. Cabral and Beaudoin, 2007; Lago et al., 1996 and references therein; Shaw et al., 1977). After careful petrographical examination of the rocks, the 53 least altered samples were selected for mineral and whole rock analyses.

Mineral compositions were determined on 30 [micro]m thick polished sections by electron microprobe (EMPA) at the Centro de Nacional Microscopia Electronica of the Complutense University (Madrid, Spain), using a JEOL JZA-8900 M electron microprobe equipped with four wavelength dispersive spectrometers. Analyses were performed using an accelerating voltage of 15 kV and an electron beam current of 20 nA, with a beam diameter of 5 [micro]m. Elemental counting times were 10 s on the peak and 5 s on each of two background positions. Analyses were corrected for electronic interactions using a ZAF procedure (atomic number (Z), absorption (A) and fluorescence (F)).

The samples selected for whole rock analyses were crushed in a manganese steel jaw-crusher and milled in an agate vibrating cup mill at the Servicios de Apoyo a la Investigation of the University of Zaragoza (Spain). Major and trace element concentrations were determined at the Service d'Analyse des Roches et des Mineraux (SARM) in Nancy (France) and the XRAL Laboratories (Canada). The samples were analysed by ICP-AES for major elements and ICP-MS for trace elements. Details on the analytical procedures and detection limits are available at http:// helium.crpg.cnrs-nancy.fr/SARM/pages/roches.html. The geochemical classification and the stratigraphic position of the selected samples are summarised in Table 2.

Data treatment was undertaken with "ad-hoc" built spreadsheets. Mineral abbreviations in the figures and the tables follow recommendations by Whitney and Evans (2010).

5. Petrography

The above described three igneous facies, defined on the basis of their field appearance, show also systematic differences under the petrographic microscope. The chilled margin facies is composed of plagioclase (50 vol. %), opaque minerals (10 vol. %) and pseudomorphed olivine (7-8 vol. %); some olivine-rich samples (up to 10 vol. %) have been recognised in the Cameros sector. This facies is vesicle-rich (30-35 vol. %); the vesicles are filled by quartz and calcite. The microstructure of this facies is aphyric to porphyritic (Fig. 5a), defined by large (up to 1.9 mm) subidiomorphic crystals of olivine replaced by secondary calcite, chlorite and opaque minerals, set in a finer-grained groundmass (150-250 [micro]m). The microcrysts of the groundmass (mainly plagioclase and opaque minerals) are widely altered to calcite and chlorite. Several xenoliths of the sedimentary host-rock (up to 15 mm in size) have been observed. They have a 100-300 [micro]m thick brown glassy rim which contains microlites of plagioclase and abundant oxides (Fig. 5b).

[FIGURE 4 OMITTED]

The central facies (Fig. 5c) is composed of plagioclase (65-70 vol. %), pseudomorphed olivine (15 vol. %), clinopyroxene (5 vol. %) and opaque minerals (5 vol. %). It shows a porphyritic to doleritic microstructure with subidiomorphic large crystals of olivine (up to 1.6 mm). The rock groundmass (7 vol. %) is composed of microcrysts of plagioclase, clinopyroxene and opaque minerals; secondary chlorite and calcite are common. Vesicles are uncommon in this facies and no xenoliths are observed.

The pegmatoid facies shows an equigranular microstructure with subidiomorphic crystals up to 1200 [micro]m (Fig. 5d). It is composed of plagioclase (75-80 vol. %), opaque minerals (10-15 vol. %), pseudomorphed olivine (5-10 vol. %) and accessory apatite.

6. Geochemistry

6.1. Mineral chemistry

Mineral compositions were determined for feldspar (Table 1), clinopyroxene (Table 1), opaque minerals and apatite. Olivine crystals are completely replaced by secondary minerals, so their original composition could not be determined.

Feldspar was analysed in samples from the central facies and the pegmatoid; in the latter, plagioclase is albitised and K-feldspar is also recognised. On the other hand, feldspar from the central facies is classified as plagioclase, with compositions ranging from labradorite to anorthoclase ([An.sub.64-14] [Ab.sub.34-73] [Or.sub.01-12]; Table 1; Fig. 6a). The analysed compositions display a typically alkaline trend of increasing orthose with decreasing anorthite (Fig. 6a).

Clinopyroxene is only present in the central facies. All the compositions are classified as Al-rich augite ([Wo.sub.43-39] [En.sub.49-39] [Fs.sub.12-22]), according to Morimoto et al. (1988); they are moderately rich in [Cr.sub.2][O.sub.3] (up to 0.58 wt. %) and Ti[O.sub.2] (up to 1.62 wt. %). The results define poor correlation trends with fractionation, represented by the decrease in mg* [mg* = Mg / (Mg+[Fe.sup.2+]+[Fe.sup.3+]+Mn)] per formula unit, p.f.u., where [Fe.sup.3+] is calculated according to Droop (1987). Si[O.sub.2], [Al.sub.2][O.sub.3], CaO and [Cr.sub.2][O.sub.3] decrease with decreasing mg*, whereas Ti[O.sub.2] increases with decreasing mg*. [Na.sub.2]O displays a significant scatter of the values. The compositions plot between the alkaline and the subalkaline fields defined by Leterrier et al. (1982; Fig. 6b).

Opaque minerals are classified as ilmenite. Their compositions vary from 55.45 to 66.19 wt. % Ti[O.sub.2] and from 33.81 to 44.55 wt. % FeOT. Apatite was only analysed in the Moncayo sector and is F-rich; its composition varies from 40.10 to 42.06 wt. % [P.sub.2][O.sub.5] and from 52.56 to 54.80 wt. % CaO.

6.2. Whole-rock chemistry

All the selected samples from the Cameros and Moncayo sectors are affected by spilitisation (Lago et al., 1989) and show variable LOI (Loss On Ignition) contents, ranging from 3.17 to 8.51 wt. % (Table 2).

The rocks of the chilled margins and the central facies are classified as tephrites, basalts, basaltic andesites and shoshonites whereas the pegmatoid facies includes the most evolved rocks: andesites and dacites (Fig. 7a). According to the Zr/Ti[O.sub.2] vs. Nb/Y diagram for altered rocks (Winchester and Floyd, 1977), most samples are classified as alkali basalts, but four of them are classified as subalkali basalts (Fig. 7b). According to the CIPW norm, the samples are plagioclase-, orthoclase-, apatite- and hypersthene-normative; most of them are also quartz-normative except for the tephrites which are olivine-normative. These results agree with the high modal proportion of plagioclase and silica contents of the rocks. The Si[O.sub.2] content varies from 41.40 wt. % in the most primitive rocks to 61.60 wt. % in the most evolved ones. The chilled margins and central facies show similar Si[O.sub.2] concentrations (41.40-53.51 wt. %), which fits well with basic to intermediate rocks. Accordingly, these samples have relatively high MgO contents (15.04-7.19 wt. %; mg#: 0.77-0.58, where mg# = MgO/(MgO+FeO)). In contrast, the pegmatoid facies comprises more evolved rocks (54.50-61.60 wt. % Si[O.sub.2]) and with lower MgO contents (8.15-5.60 wt. %; mg#: 0.66-0.54). None of the analysed samples (Table 2) presents compositional features typical of primitive magmas in equilibrium with their mantle source (which typically show MgO > 11 wt. %, Cr > 500-1000 ppm and Ni > 200-500 ppm; Frey et al, 1978).

[FIGURE 5 OMITTED]

The variability in whole-rock major element abundances is illustrated using MgO variation diagrams (Fig. 8). Generally, there is a wider scatter of major element distributions. However, some poor correlations can be established. [Fe.sub.2][O.sub.3]t behaves compatibly and shows a decrease in abundance with the decreasing MgO (Fig. 8), whereas Si[O.sub.2] Ti[O.sub.2] and[Na.sub.2]O increase with the decreasing of MgO (Fig. 8). [Al.sub.2][O.sub.3], MnO, CaO, [K.sub.2]O and [P.sub.2][O.sub.5] abundances are relatively constant or scatter at varying MgO contents (not shown). LOI values are higher in the chilled margins and central facies, probably related to the high alteration degree shown by olivine and clinopyroxene crystals. Fig. 9 shows a slightly compatible behaviour of the transition elements (Cr, Ni) and a scattering of the large ion lithophile elements (LILE) and high field strength elements (HFSE). The light rare earth (LREE) and medium rare earth elements (MREE) show a general incompatible behaviour (Fig. 9), whereas the heavy rare earth elements (HREE), U and Th display a relative scattering, probably related to the presence of apatite in these rocks.

[FIGURE 6 OMITTED]

The high degree of alteration (Table 2) suggests that subsolidus processes may have played an important role in the final whole rock composition. The LILE and HFSE are highly mobilised during spilisation (e.g. Lago et al., 1989 and references therein; Shaw et al., 1977). Therefore, inmobile incompatible elements are preferred to define the geochemical affinity of these rocks. The Nb/Y ratios range between 0.44-1.89 (Table 2) indicating an alkaline affinity, in agreement with the orthose enrichment of the most albitic plagioclase (Fig. 6a). Moreover, Ti/V ratios range between 42 and 99 (Table 2), as typical for alkali basalts and oceanic island basalts (Shervais, 1982).

[FIGURE 7 OMITTED]

The chilled margin and central facies display the lowest REE abundances, whereas the pegmatoid facies presents the highest ones (Table 2). The primitive mantlenormalised incompatible ratios [(La/Yb).sub.N] are similar in the chilled margin and central facies (2.32-14.55; Table 2) and are higher for the rocks of the pegmatoid facies (12.95-26.99; Table 2). The primitive mantle-normalised multielemental patterns are rather similar to each other (Fig. 10). The most incompatible elements are 10 to 200 times enriched over the primitive mantle. Most of the samples present strong Sr and Zr negative anomalies and enrichments in U and K. Furthermore, Rb, Ba, Ti and Eu display a relative variability. Finally, the LREE display subparallel patterns and the HREE show an increasing slope from chilled margin and central facies to the pegmatoid facies.

[FIGURE 8 OMITTED]

7. Discussion

7.1. Emplacement and age of the magmatism

The igneous bodies are usually concordant to bedding planes, so they can be considered sill-like bodies. In the outcrops of the Moncayo sector only one igneous body (sill) is recognised. On the other hand, in the outcrops of the Cameros sector several igneous bodies are exposed. Sometimes, the igneous bodies are separated by thin sedimentary beds of argillites. In other cases, there is no separation in between and the sequence chilled margin--central facies is repeated several times. Therefore, they could belong to a single sill, sometimes filled by multiple pulses of magma. In each sector, the igneous outcrops cannot be clearly related to each other due to their considerable geographical dispersion. Accordingly, the occurrence of one or several sills per sector cannot be ascertained.

[FIGURE 9 OMITTED]

Bastida et al. (1989) described a low-grade contact metamorphism in the host-rocks of the Moncayo sector, related to the emplacement of the sills. The thickness of the sills in this sector ranges between 0.6 and 38 m. In the latter case, according to the heat transfer approximation by Jaeger (1968) and considering a thermal diffusivity of [10.sup.-6] [m.sup.2]/s (Huppert and Sparks, 1980), the sill started cooling 42 days after the emplacement of the magma and 418 days were needed to cool the centre of the sill. These results suggest a slow cooling rate, compatible with the development of the contact metamorphism in the sedimentary host-rock. The greater thickness of the sills in the Cameros sector (between 2 and 94 m) indicates even slower cooling rates; therefore, the development of contact metamorphism in this area cannot be ruled out.

The contacts of the sills are irregular and characterised by a peperitic transition zone (Fig. 4b). Peperites are typically developed where magma has come into contact with unconsolidated, wet sediments (Befus et al, 2009; Kano, 1991; Kano, 2002; Kokelaar, 1982; Lavine and Aalto, 2002; Leat and Thompson, 1988; Nemeth and Martin, 2007; Walker, 1992). The presence of sediment injections and irregular fragments of structure-less sediment at the lower contact of the sills (Fig. 4b and 4c) indicate that the unconsolidated host sediments were remobilised and injected through fractures into the sill and subsequently baked by contact metamorphism (Bastida et al., 1989; Busby-Spera and White, 1987; Gifkins et al., 2002; Kokelaar, 1982). The presence of vesicles trapped in the thickest igneous levels indicates that the magma emplaced into shallow and unconsolidated sediments.

[FIGURE 10 OMITTED]

The considerable alteration of the rocks (Table 2) prevents carrying out radiometric datings. However, the following field relationships are good indicators of the age of the igneous rocks: 1) first of all, the sills emplaced into the Keuper facies: 2), both the sills and the sedimentary host-rocks are affected by the Alpine deformation (e.g., Casas Sainz and Gil-Imaz, 1998; Guimera et al., 2004), constraining the emplacement age of the sills to the Mesozoic; 3) in the Moncayo sector the conglomerates of the upper part of the Keuper facies include clasts of igneous rocks petrologically equivalent to the sills emplaced in the middle part of the Keuper facies (Lago et al., 1996), indicating an erosive and sedimentary phase between the emplacement of the sills and the sedimentation of the upper part of the Keuper facies; 4) the injections of sediment and the fragments of structure-less sediment from the host-rocks inside the sills, together with the development of peperites, as a whole indicate that the magma emplaced into wet, unconsolidated sediments. These arguments imply that the sills were emplaced during or shortly after the deposition of the Keuper facies sediments. Hence, the age of this magmatism can be defined as Upper Triassic.

Several differences between the emplacement styles of the igneous rocks in the two studied sectors can be highlighted. Firstly, the volume of exposed igneous rocks increases from the Moncayo sector (maximum thickness: 38 m) to the Cameros sector (maximum thickness: 94 m). Furthermore, in the outcrops of the Cameros sector multiple sills are recognised, in contrast with the single sills of the Moncayo sector. This difference suggests several pulses of magma in the Cameros sector and a single pulse in the Moncayo sector. Besides, the upper part of the Keuper facies is formed by a thin (up to 7 m thick) and homogeneous lacustrine sedimentary sequence in the Cameros sector, whereas it comprises an irregular alluvial-fluvial conglomeratic sequence related to an emerged continental area in the Moncayo sector. The spatial thickness variation of the conglomerate unit of the Moncayo sector and the size of its clasts suggest a proximal area located in the western part and the distal area located in the eastern part of this sector. The SW-NE main directions of the channel-shaped surfaces measured in the field suggest a possible source area close to the Tablado-Jarque fault. This is in agreement with the absence of the conglomeratic unit in the westermost outcrop of the Moncayo sector (section 11; Fig. 3b), located at the hangingwall of this main Variscan fault.

Considering all the igneous outcrops, the volume of emplaced magma gradually increases from the SE to the NW (from Moncayo to Cameros). Furthermore, three areas of maximum thickness of exposed igneous rocks can be identified (Fig. 11): Cameros, Beraton and Arandiga (the latter two located in the Moncayo sector); these areas could be related to magma emission centres.

According to the exposed igneous thicknesses (Fig. 11), a close relationship between the distribution of the igneous rocks and the main fracture systems at a regional scale can be established (i.e. the Datos and the related Tablado-Jarque fault system; Fig. 2). Concerning the Cameros sector, the magma emplacement could be related to a master late-Variscan normal fault, corresponding to the present-day northern Cameros thrust (Casas Sainz and Gil-Imaz, 1998). On the other hand, the magma emplacement in the Moncayo area probably rose through a set of faults related to the master Datos fault (Fig. 2). Accordingly, it is suggested that the main magma emplacement in the NW sector of the Iberian Rift was probably linked to first-order late-Variscan normal faults.

[FIGURE 11 OMITTED]

[FIGURE 12 OMITTED]

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7.2. Petrologic constraints and source of the magmatism

Based on field and petrographic relationships we have identified three facies in the studied sills: chilled margins, central facies and pegmatoids. All the facies have a similar mineralogy, although clinopyroxene has only been recognised in the central facies. However, the modal proportions vary from the chilled margin and central facies to the pegmatoid as follows: olivine decreases and plagioclase increases. Regarding the geochemical results, the chilled margins and the central facies show the most primitive compositions (lower Si[O.sub.2] and higher MgO contents; Table 2) whereas the pegmatoids present the most evolved compositions. Therefore, the distribution of the identified facies is related to a normal differentiation process from the margins of the sills inwards. The enrichments in Si[O.sub.2], Ti[O.sub.2], [Na.sub.2]O and incompatible trace elements (e.g., REE) in the pegmatoid are consistent with these rocks having crystallised from late-stage, more evolved melts. The differentiation process agrees with the slow cooling rate of the sills (more than 400 days) due to their large thickness.

The subsolidus processes (spilitisation) probably have substantially changed the original whole-rock composition, as revealed by the high value of LOI (Table 2) probably related to the replacement of original mineralogy by secondary minerals. This hypothesis is consistent with the presence of vesicles filled with quartz and chlorite. The subsolidus processes, together with the frequent host-rock xenoliths, could explain the anomalous enrichment in Si[O.sub.2] in these basic to intermediate rocks. Due to this extensive alteration and contamination, the mantle source of this magmatism is very hard to unravel. Nevertheless, some information can be drawn from the immobile trace elements.

The primitive mantle-normalised trace element patterns show a relative depletion in Nb and Ta (Fig. 10). This feature is characteristic of subduction-related melts or magmas affected by crustal contamination (Dupuy and Dostal, 1984; Dostal et al., 1986; Thompson et al., 1984). Nb/U ratios show an average value of 13 (Table 2) which is similar to the mean value of the continental crust and the island arc rocks (Nb/U ~ 10; Hofmann, 1997) and significantly lower than the value for OIB and MORB derived-rocks (Nb/U ~ 47; Hofmann, 1997). The K and U enrichments (Fig. 10) also support the crustal contamination of the magmas.

0n the Th/Yb versus Ta/Yb diagram (Fig. 12a), the studied rocks plot within the mantle array between the OIB and the E-MORB compositions, suggesting the participation of an enriched subcontinental mantle source (Hawkesworth et al., 1983; Menzies et al., 1983; Morata et al., 1997, among others). Some of the samples have Th/ Yb ratios more enriched than the OIB ratios suggesting crustal contamination. Similar conclusions can be drawn from the La/10, Y/15, Nb/8 triangular diagram (Fig. 12b) of Cabanis and Lecolle (1989), where the data plot between the alkaline and the E-MORB fields; in this diagram, the compositions are scattered and slightly enriched in the La/10 ratio, supporting crustal contamination.

7.3. Comparison with other Upper Triassic magmatisms of southwestern Europe: geodynamic implications

The Upper Triassic alkaline magmatic province of southwestern Europe was developed at the end of the Triassic rift stage and comprises outcrops in four sectors: NW part of the Iberian Range, south of the Catalonian Coastal Ranges, North Range of Mallorca and SE France (Corbieres, Ecrins-Pelvoux and Provence; Azambre and Fabries, 1989; Lago et al., 1996). This magmatic province was defined according to: 1) the similar mineralogical (olivine, Ti-rich augite, plagioclase and opaque minerals) and geochemical composition of the exposed rocks; 2) their alkaline affinity and 3) the presence of ultramafic xenoliths (Azambre and Fabries, 1989, Lago et al., 1996). However, some differences between the outcrops of the NW part of the Iberian Chain and those of the other sectors of this province are identified. Firstly, the rocks of the NW part of the Iberian Chain have more evolved compositions (basalts to dacites), higher degrees of alteration (Table 2) and no peridotite xenoliths. Secondly, only subvolcanic rocks (sills) are recognised in the NW part of the Iberian Chain whereas subvolcanic rocks (sills and dikes) and phreatomagmatic rocks crop out in the other sectors of the province (Azambre and Rossy, 1981, Durand et al., 2011 and references therein, Mitjavila and Marti, 1985; Navidad and Alvaro, 1985; Sanz et al., 2012b, Vatin-Perignon et al., 1974). Finally, the rocks exposed in the NW part of the Iberian Chain show geochemical evidences of the participation of an enriched subcontinental mantle source and a slight crustal contamination (Fig. 12a and b), whereas the rocks of the southern part of the Catalonian Coastal Ranges, the North Range of Mallorca and the Corbieres in SE of France suggest an asthenospheric mantle source with no significant crustal contamination (Fig. 12a and b).

Apart from the alkaline magmatic province proposed by Azambre and Fabries (1989) and Lago et al. (1996), other Upper Triassic magmatisms (late Carnian to Norian) related to the Triassic rift have been recognised in the external part of the Betic Cordillera (Perez-Lopez et al., 2012) and in the Brescian Prealps (Cassinis et al., 2008). The magmatism described in the Betic Cordillera emplaced into the Zamoranos Fm (Perez-Lopez et al., 1992), which is correlated to the Imon Fm of the Iberian Chain (Perez-Lopez et al., 1992; Lopez-Gomez et al., 1998; Arnal et al., 2002). The rocks are strongly altered and show field evidences of magma-sediment interaction, as the rocks of the northwestern Iberian Chain. According to Perez-Lopez et al. (2012), this magmatism is represented by sub-alkaline basalts to basaltic andesites deriving from a subcontinental upper mantle with assimilation of continental crust. A similar source has been inferred for the Late Carnian magmatism of the Brescian Prealps (Cassinis et al., 2008). These data suggest a likely similar mantle source and crustal contamination processes for the magmatisms of the NW part of the Iberian Chain, the external parts of the Betic Cordillera and the Brescian Prealps. However, no geochemical data are available for these sectors and a deep study would be necessary to prove this hypothesis.

The paleogeographic reconstruction of the western part of the Neotethys Realm during the Late Triassic shows an extensive epicontinental platform which correspond to the Imon Fm and other equivalent units (Fig. 13). The magmatism of this period is characterised by an asthenospheric source in the southeastern (inner) parts of the shallow platform (Catalonian Coastal Ranges and southern France) and by a progressively more sub-lithospheric mantle with a greater crustal contamination towards the western and northern (litoral) parts of this platform (NW Iberian Chain -this study-, External Betics and Brescian Prealps). These differences can be related to the thickness of the crust, which had to be thinner at the southeastern parts, allowing the melting of a deeper (asthenospheric) mantle. This is in agreement with the presence of ultramafic xenoliths only in the southeastern parts (Azambre and Fabries, 1989, Lago et al., 1996; Sanz et al., 2012b). On the other hand, a thicker crust in the western and northern parts of the Neotethys realm conditioned the melting of a shallower sublithospheric mantle (E-MORB) and favoured the crustal contamination processes. A common geodynamic scenario for the Iberian Chain and the External Betics is consistent with the location of the Betic-Rif Cordillera and other terranes between the Iberian Peninsula and southern France until the Oligocene, as suggested by Rosenbaum et al. (2002 and references therein).

8. Conclusions

The Upper Triassic magmatism of the northwestern Iberian Chain is represented by sills of decametric thickness cropping out in two sectors: Cameros and Moncayo. This magmatism is characterised by a strong alteration (spilitisation) triggering mobilisation of LILE and HFSE. According to the interaction processes recognised between the magma and the host sediments, the emplacement of the magma took place during or shortly after the deposition of the Keuper facies. The presence of a conglomerate unit overlaying the sills in the Moncayo sector that contains clasts of similar igneous rocks strongly supports an Upper Triassic age for this magmatism.

The important thickness of the sills conditioned a slow cooling of the magma, triggering contact metamorphism of the host sediments and an internal differentiation of the magma bodies. From the sill margins inwards it shows: chilled margins, central facies and pegmatoid facies.

The source of this magmatism is inferred to be an enriched subcontinental mantle source involving an EMORB component. The role of crustal contamination of the melts is clearly recognised. These source characteristics disagree with those recognised for other Upper Triassic magmatisms in northeastern Iberia and SE France. In contrast, similar rocks are found in the external Betic Cordillera and the Brescian Prealps. In the paleogeographical context of the Iberian plate in the Upper Triassic, the outcrops located in the inner platform area (Catalonian Coastal Ranges and SE France) present a deeper (asthenospheric) mantle source probably related to a thinner crust. On the contrary, the outcrops located in the outer platform (litoral) area (NW Iberian Chain -this study-, External Betics and Brescian Prealps) are characterised by a shallower, lithospheric mantle source involving crustal contamination.

http://dx.doi.org/10.5209/rev_JIGE.2013.v39.nl.41759

Acknowledgements

We thank reviewers A. Ronchi and D. Gimeno and editors J. Lopez-Gomez and J. Martin-Chivelet for their constructive comments which improved the original manuscript. The present work was financially supported by the 2010-edition of Research Grants of the IER (Instituto de Estudios Riojanos) of La Rioja Government, trough the project "Triassic magmatisms of the N Cameros Massif (La Rioja): environmental implications".

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T. Sanz, M. Lago, A. Gil, C. Gale *, J. Ramajo, T. Ubide, A. Pocovl, P. Tierz, P. Larrea

Earth Sciences Department, University of Zaragoza, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain

* corresponding autor: carlos.gale@gmail.com

Received: 29/08/2012/Accepted: 08/12/2012
Table 1.--Representative major element composition (expressed as
wt.%) of minerals from the studied igneous rocks. Structural
formulae calcu-lated to 8 (Pl) and 6 (Cpx) oxygens. [Fe.sup.3+]
was calculated using Droop (1987) algorithm.

Tabla 1.-Composiciones en elementos mayores representativas
(expre-sadas en % en peso) de minerales de las rocas lgneas
estudiadas. For-mula estructural calculada a 8 (Pl) y 6 (Cpx)
oxigenos. [Fe.sup.3+] calculado mediante el algortimo de Droop
(1987).

Mineral                                     Pl                 Cpx

Type                    rim      core       rim      core      core

Si[O.sub.2]            64.13     52.76     64.78     63.05     51.77
Ti[O.sub.2]            0.16      0.07      0.07      0.11      1.29
[Al.sub.2][O.sub.3]    21.40     29.90     21.59     22.55     2.68
[Cr.sub.2][O.sub.3]    n.a.      n.a.      n.a.      n.a.      0.58
MgO                    0.54      0.15      0.22      0.05      15.77
Fe[O.sub.1]            0.57      0.49      0.49      0.57      7.58
NiO                    0.00      0.01      0.00      0.05      0.05
MnO                    0.00      0.00      0.00      0.00      0.09
CaO                    3.22      12.52     3.01      4.17      20.00
[Na.sub.2]O            7.08      4.20      8.47      8.08      0.29
[K.sub.2]O             3.88      0.27      2.19      2.01      0.00
BaO                    0.00      0.00      0.00      0.00      n.a.
Total                 100.98    100.37    100.82    100.64    100.10

Si                     2.84      2.39      2.86      2.80      1.91
Ti                     0.01      0.00      0.00      0.00      0.04
Al                     1.12      1.59      1.12      1.18      0.12
Cr                      --        --        --        --       0.02
[Fe.sup.3+]             --        --        --        --       0.00
Mg                     0.04      0.01      0.01      0.00      0.87
[Fe.sup.2+]             --        --        --        --       0.23
[Fe.sup.1]             0.02      0.02      0.02      0.02       --
Ni                     0.00      0.00      0.00      0.00      0.00
Mn                     0.00      0.00      0.00      0.00      0.00
Ca                     0.15      0.61      0.14      0.20      0.79
Na                     0.61      0.37      0.72      0.70      0.02
K                      0.22      0.02      0.12      0.11      0.00
Ba                     0.00      0.00      0.00      0.00       --
Total                   5.0       5.0       5.0       5.0       4.0

An                      16        61        14        20        --
Ab                      62        37        73        69        --
Or                      22         2        12        11        --
En                      --        --        --        --        46
Fs                      --        --        --        --        13
Wo                      --        --        --        --        42
mg#                     --        --        --        --        79

Mineral                           Cpx
Type                     >         >        rim

Si[O.sub.2]            51.37     50.51     50.87
Ti[O.sub.2]            1.51      1.54      1.51
[Al.sub.2][O.sub.3]    2.36      2.23      1.45
[Cr.sub.2][O.sub.3]    0.13      0.07      0.05
MgO                    15.43     14.69     13.45
Fe[O.sub.1]            9.89      11.59     13.43
NiO                    0.05      0.05      0.03
MnO                    0.14      0.15      0.17
CaO                    19.01     18.42     18.96
[Na.sub.2]O            0.26      0.32      0.26
[K.sub.2]O             0.00      0.01      0.00
BaO                    n.a.      n.a.      n.a.
Total                 100.15     99.58    100.18

Si                     1.91      1.90      1.92
Ti                     0.04      0.04      0.04
Al                     0.10      0.10      0.06
Cr                     0.00      0.00      0.00
[Fe.sup.3+]            0.00      0.03      0.02
Mg                     0.85      0.82      0.76
[Fe.sup.2+]            0.30      0.33      0.41
[Fe.sup.1]              --        --        --
Ni                     0.00      0.00      0.00
Mn                     0.00      0.00      0.01
Ca                     0.76      0.74      0.77
Na                     0.02      0.02      0.02
K                      0.00      0.00      0.00
Ba                      --        --        --
Total                   4.0       4.0       4.0

An                      --        --        --
Ab                      --        --        --
Or                      --        --        --
En                      44        43        39
Fs                      16        19        22
Wo                      39        38        39
mg#                     73        69        64

Table 2.-Major element (wt.%) and trace element (ppm) composition
of selected samples from studied igneous rocks.

Tabla 2.-Composition en elementos mayores (% en peso) y traza
(ppm) de muestras seleccionadas de las rocas Igneas estudiadas.

Referencia            281-4-C3   281-1-C9   281-1-D2   281-1-F2
Rock Type             Bas And    Bas And    Bas And      And
Facies                  Cen        Cen        Cen        Cen
Section                 out         2          2          3

Si[O.sub.2]            51.90      50.60      52.20      53.20
Ti[O.sub.2]             1.63       1.63       1.67       1.41
[Al.sub.2][O.sub.3]    14.07      15.36      14.66      14.72
[Fe.sub.2][O.sub.3]    10.42       8.62       8.48       8.23
MnO                     0.02       0.03       0.05       0.03
MgO                    10.50       7.63       7.19      10.30
CaO                     1.12       5.85       5.82       1.69
[Na.sub.2]O             0.17       2.30       2.52       2.86
[K.sub.2]O              4.44       1.07       1.19       1.41
[P.sub.2][O.sub.2]      0.34       0.40       0.43       0.37
LOI                     5.62       5.94       5.76       6.81
mg *                    0.70       0.67       0.66       0.74
TOTAL                  100.23     99.43      99.97      101.03

Li                      125         52         62        372
Rb                       54         13         20         10
Cs                      n.a.       n.a.       n.a.       n.a.
Be                      n.a.       n.a.       n.a.       n.a.
Sr                       25        247        292        105
Ba                      166        158        219        215
Sc                       22         22         20         20
V                       173        207        187        187
Cr                      211        216        240        227
Co                       50         64         60         55
Ni                      134        157        154        149
Cu                       8          29         16         30
Zn                       29         42         40        140
Ga                       19         16         19         19
Y                        10         17         18         15
Nb                       8          14         19         13
Ta                      n.a.       n.a.       n.a.       n.a.
Zr                      23.0       89.0      119.0       51.0
Hf                      n.a.       n.a.       n.a.       n.a.
Mo                      n.a.       n.a.       n.a.       n.a.
Sn                      n.a.       n.a.       n.a.       n.a.
Tl                      n.a.       n.a.       n.a.       n.a.
Pb                      n.a.       n.a.       n.a.       n.a.
U                       0.50       0.50       0.90       0.90
Th                      1.20       1.90       2.50       1.50
La                     12.90      12.10      16.90       9.90
Ce                     26.50      24.80      33.00      21.00
Pr                      3.50       3.10       4.10       2.80
Nd                     17.50      14.50      19.20      13.80
Sm                      4.10       3.50       3.90       3.40
Eu                      1.14       1.12       1.42       0.76
Gd                      3.40       3.30       4.10       3.60
Tb                      0.50       0.50       0.60       0.50
Dy                      2.30       2.90       3.30       2.80
Ho                      0.36       0.60       0.62       0.52
Er                      0.90       1.70       1.80       1.50
Tm                      0.10       0.20       0.20       0.20
Yb                      0.60       1.10       1.30       1.00
Lu                      0.09       0.20       0.20       0.15

Nb/Y                    0.80       0.82       1.06       0.87
(La/Yb) n              14.55       7.45       8.80       6.70
(La/Sm) n               1.98       2.18       2.73       1.84
Ti/V                     56         47         54         45

Referencia             FIT-X    AGR-P     AGR-7    AGR-23    281-4-C1
Rock Type             Bas And    Teph    Bas And    Shos     Bas And
Facies                  Cen      Cen       Cen       Cen       Bor
Section                  9        11       11        11        out

Si[O.sub.2]            52.08    41.43     53.00     50.50     50.40
Ti[O.sub.2]            2.35      1.84     1.45      1.57       1.61
[Al.sub.2][O.sub.3]    12.84    14.96     15.05     14.33     12.75
[Fe.sub.2][O.sub.3]    9.16     11.27     7.91      10.41     11.00
MnO                    0.02      0.02     0.02      0.03       0.02
MgO                    8.08     11.36     10.75     8.96      15.04
CaO                    2.99      3.40     0.86      1.80       0.55
[Na.sub.2]O            2.73      0.08     2.98      1.87       0.12
[K.sub.2]O             2.00      6.45     2.04      4.48       1.91
[P.sub.2][O.sub.2]     0.32      0.26     0.30      0.35       0.48
LOI                    6.59      7.90     5.11      5.00       6.96
mg *                   0.67      0.70     0.76      0.66       0.76
TOTAL                  99.15    98.96     99.47     99.30     100.84

Li                      n.a      n.a.      142       76        192
Rb                      23        68       21        54         17
Cs                       0        0         0         0        n.a.
Be                       1        1         0         0        n.a.
Sr                      126       42       48        75         11
Ba                      311      223       140       350        50
Sc                      n.a      n.a.      23        23         17
V                       182      265       173       204       181
Cr                      141      281       197       258       220
Co                      29        37       56        57         57
Ni                      104      140       134       156       148
Cu                       6        7         6         6         7
Zn                      22        22       27        25         30
Ga                      16        17       20        19         17
Y                       25        17       14        14         9
Nb                      19        15        8         9         17
Ta                      1.4      1.1      n.a.      n.a.       n.a.
Zr                     156.5    122.6     21.0      24.0       14.0
Hf                     3.99      3.13     n.a.      n.a.       n.a.
Mo                     1.47      0.88     n.a.      n.a.       n.a.
Sn                     1.68      1.34     n.a.      n.a.       n.a.
Tl                     0.00      n.a.     n.a.      n.a.       n.a.
Pb                     2.60      1.93     n.a.      n.a.       n.a.
U                      1.02      2.49     0.50      0.60       2.60
Th                     2.64      1.99     1.10      1.10       1.90
La                     13.30     7.25     7.20      9.60       6.90
Ce                     28.68    15.35     17.20     20.40     13.70
Pr                     3.78      2.13     2.50      2.90       1.70
Nd                     16.70     9.68     11.40     14.00      8.50
Sm                     4.41      2.86     3.40      3.70       2.70
Eu                     1.25      0.87     0.99      1.41       0.95
Gd                     4.78      3.18     3.70      3.70       2.90
Tb                     0.79      0.53     0.60      0.60       0.50
Dy                     4.78      3.15     3.00      3.30       2.10
Ho                     0.93      0.62     0.50      0.54       0.37
Er                     2.47      1.72     1.40      1.40       1.00
Tm                     0.36      0.25     0.10      0.10       0.10
Yb                     2.23      1.65     0.70      0.80       0.60
Lu                     0.32      0.25     0.09      0.11       0.08

Nb/Y                   0.76      0.86     0.57      0.64       1.89
(La/Yb) n              4.03      2.98     6.96      8.12       7.78
(La/Sm) n              1.90      1.60     1.34      1.64       1.61
Ti/V                    77        42       50        46         53

Referencia            281-1-TS1   CAV-2     AGR-1    AGR-3    AGR-28
Rock Type              Bas And     Shos    Bas And    Bas      Shos
Facies                   Bor       Bor       Bor      Bor      Bor
Section                   3         11       11        11       11

Si[O.sub.2]             49.62     53.51     51.00    48.00    51.50
Ti[O.sub.2]             1.69       1.39     1.65      1.43     1.56
[Al.sub.2][O.sub.3]     14.76     12.83     12.93    13.30    14.60
[Fe.sub.2][O.sub.3]     7.36      13.87     8.54     14.22     7.64
MnO                     0.02       0.02     0.04      0.03     0.03
MgO                     11.04      8.53     10.27    11.68    11.41
CaO                     2.65       0.46     2.96      0.50     1.09
[Na.sub.2]O             1.89       0.29     1.78      0.82     0.78
[K.sub.2]O              2.10       5.61     2.38      3.42     4.95
[P.sub.2][O.sub.2]      0.27       0.19     0.44      0.35     0.26
LOI                     8.51       4.34     7.51      5.67     6.01
mg *                    0.77       0.58     0.73      0.65     0.77
TOTAL                   99.91     101.03    99.50    99.42    99.83

Li                       n.a       n.a.      150      140      131
Rb                       25         55       26        33       50
Cs                        1         0       n.a.      n.a.     n.a.
Be                        1         1       n.a.      n.a.     n.a.
Sr                       76         25       37        21       18
Ba                       174       200       165      134      145
Sc                       n.a       n.a.      21        20       22
V                        179       149       217      188      175
Cr                       278       218       207      172      201
Co                       29         35       56        61       57
Ni                       143       138       130      170      140
Cu                        6         6         7        9        5
Zn                       140        23       21        34       27
Ga                       20         16       18        19       20
Y                        20         20       18        13       14
Nb                       19         9        15        10       10
Ta                       1.4       0.6      n.a.      n.a.     n.a.
Zr                      131.2      86.2     18.0      30.0     20.0
Hf                      3.26       2.27     n.a.      n.a.     n.a.
Mo                      0.84       0.79     n.a.      n.a.     n.a.
Sn                      1.62       1.13     n.a.      n.a.     n.a.
Tl                      n.a.       n.a.     n.a.      n.a.     n.a.
Pb                      1.56       1.11     n.a.      n.a.     n.a.
U                       1.21       2.02     1.90      2.00     0.50
Th                      2.93       1.66     1.90      1.70     1.00
La                      11.23      5.98     14.00     8.40     4.80
Ce                      24.19     12.63     27.30    18.20    14.20
Pr                      2.97       1.73     3.70      2.40     2.70
Nd                      12.53      7.90     17.40    12.10    16.00
Sm                      3.03       2.70     4.40      4.20     4.90
Eu                      0.80       0.95     1.36      1.28     1.98
Gd                      3.31       3.47     5.00      4.60     4.70
Tb                      0.58       0.62     0.80      0.70     0.70
Dy                      3.73       3.83     4.10      3.20     3.50
Ho                      0.73       0.74     0.71      0.52     0.53
Er                      1.93       1.99     1.90      1.50     1.30
Tm                      0.27       0.28     0.20      0.20     0.10
Yb                      1.67       1.75     1.10      0.90     0.70
Lu                      0.24       0.26     0.14      0.12     0.08

Nb/Y                    0.98       0.44     0.83      0.77     0.71
(La/Yb) n               4.56       2.32     8.62      6.32     4.64
(La/Sm) n               2.34       1.40     2.01      1.26     0.62
Ti/V                     56         56       46        46       53

Referencia            352-3-20   BER-1    AGR-13    352-3-I2
Rock Type               Teph      Teph    Bas And     Dac
Facies                  Bor       Bor      Pegm       Pegm
Section                  13        14       11         13

Si[O.sub.2]            41.40     44.77     54.50     61.60
Ti[O.sub.2]             1.96      1.93     2.51       3.32
[Al.sub.2][O.sub.3]    14.30     14.97     11.37     11.80
[Fe.sub.2][O.sub.3]    16.54     10.13     13.75      6.65
MnO                     0.02      0.01     0.02       0.01
MgO                    13.55     10.23     7.05       5.60
CaO                     0.83      3.09     0.97       0.91
[Na.sub.2]O             1.54      0.06     3.62       2.00
[K.sub.2]O              3.72      6.58     1.91       4.20
[P.sub.2][O.sub.2]      0.39      0.34     0.68       0.42
LOI                     5.94      7.20     3.98       3.17
mg *                    0.65      0.70     0.54       0.66
TOTAL                  100.19    99.32    100.36     99.68

Li                      124       n.a.      68         80
Rb                       46        56       22         45
Cs                      n.a.       0         0         0
Be                      n.a.       0         0         0
Sr                       21        53       84         68
Ba                      181       210       146       264
Sc                       19       n.a.      18         18
V                       246       212       188       202
Cr                      244       599       33         32
Co                       52        33       60         54
Ni                      166       121       107        90
Cu                       10        22       42         10
Zn                       26        32       32         18
Ga                       21        17       18         14
Y                        10        19       13         12
Nb                       10        14        7         19
Ta                      n.a.      0.9      n.a.       n.a.
Zr                      16.0     113.7     23.0       29.0
Hf                      n.a.      3.00     n.a.       n.a.
Mo                      n.a.      0.98     n.a.       n.a.
Sn                      n.a.      1.41     n.a.       n.a.
Tl                      n.a.      n.a.     n.a.       n.a.
Pb                      n.a.      0.94     n.a.       n.a.
U                       1.90      3.43     0.30       1.90
Th                      2.70      1.85     1.50       2.60
La                     14.00      7.06     15.30     17.50
Ce                     26.80     13.86     30.50     34.00
Pr                      3.60      2.14     4.30       4.60
Nd                     16.10     10.01     20.20     21.30
Sm                      4.30      3.32     4.90       5.10
Eu                      1.29      0.91     1.43       1.31
Gd                      4.40      3.85     4.30       5.00
Tb                      0.60      0.60     0.60       0.60
Dy                      3.10      3.45     3.00       3.20
Ho                      0.48      0.63     0.52       0.50
Er                      1.30      1.63     1.30       1.10
Tm                      0.20      0.22     0.20       0.20
Yb                      0.70      1.32     0.80       0.80
Lu                      0.09      0.19     0.09       0.09

Nb/Y                    1.00      0.73     0.54       1.58
(La/Yb) n              13.54      3.61     12.95     14.81
(La/Sm) n               2.05      1.34     1.97       2.16
Ti/V                     48        55       80         99

Referencia            352-3-I6
Rock Type               And
Facies                  Pegm
Section                  13

Si[O.sub.2]            57.40
Ti[O.sub.2]             3.00
[Al.sub.2][O.sub.3]    12.59
[Fe.sub.2][O.sub.3]    10.34
MnO                     0.12
MgO                     8.15
CaO                     0.89
[Na.sub.2]O             2.70
[K.sub.2]O              1.00
[P.sub.2][O.sub.2]      0.44
LOI                     3.30
mg *                    0.64
TOTAL                  99.93

Li                       73
Rb                       41
Cs                       0
Be                       0
Sr                       53
Ba                      250
Sc                       20
V                       198
Cr                      155
Co                       82
Ni                      347
Cu                      150
Zn                      117
Ga                       13
Y                        14
Nb                       22
Ta                      n.a.
Zr                      37.0
Hf                      n.a.
Mo                      n.a.
Sn                      n.a.
Tl                      n.a.
Pb                      n.a.
U                       2.30
Th                      3.00
La                     31.90
Ce                     61.80
Pr                      8.10
Nd                     36.60
Sm                      8.00
Eu                      1.94
Gd                      6.40
Tb                      0.80
Dy                      3.30
Ho                      0.52
Er                      1.40
Tm                      0.10
Yb                      0.80
Lu                      0.10

Nb/Y                    1.57
(La/Yb) n              26.99
(La/Sm) n               2.52
Ti/V                     91
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Title Annotation:texto en ingles
Author:Sanz, T.; Lago, M.; Gil, A.; Gale, C.; Ramajo, J.; Ubide, T.; Pocovl, A.; Tierz, P.; Larrea, P.
Publication:Journal of Iberian Geology
Date:Jul 1, 2013
Words:11468
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